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The presence of pure white and pure
black can be assessed using the high and
low value bands attached to each negative,
as described in
Step 4,
Each print should be evaluated for
exposure, development, and contrast.
Variability among prints maybe caused by
changes in
- Paper, chemicals, or processing
- Intensity or color of light source
- Effective density of the negative
due to fading, or drying
Without the scales attached to each
print, subtile deviations from the optimum
will go unnoticed. The most troublesome
for me are #2 and #3, light intensity
being a continuous problem, and the
fading of the
negative most noticeable within
the first few weeks.
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The density scales on
each properly made print should
exhibit the following
characteristics.
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Loss of
Contrast
Clue: White band has no white, as
easily seen against the taped portion,
while the low value (black) scale exhibits
the expected density. Since the contrast
is controlled by both density AND color in the
negative, I would be at a loss to know
which has caused the loss of "effective
density". The most direct fix for this
problem is to add a bit of magenta when
printing.
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Excessive
Exposure
Clue: Too much density in both the high
AND low value
scales. If all of the normal procedures
have been followed, this is most likely
due to an unstable light source and
requires checking with a light probe such
as the
Ilford
EM10.
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The
Specific Problem
of Negative Fading
Since the calibration process is
usually carried out with negatives that
have just been printed, the "effective
density" is provided by "fresh" ink. Does
the effective density change as the ink
dries? It now appears the answer is YES! Prints made with
negatives that are 2 to 3 weeks old,
exhibit the tonality shown in the "Loss of
Contrast" example above. Black is fine,
but white is no longer white, indicating
that HUE=0 and a
Transfer Function setting of 70 does not
provide adequate contrast after the
negative has aged.
Rather than change the initial negative
color, I have chosen to add magenta to the
light source, and add exposure time. This
means a bit of print testing at each new
session, but perhaps the degradation will
slow or stop after the first few days.
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Light Source
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"Fresh" negative
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White
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"Aged" negative
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~ 30cc Magenta
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Home
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Preparation
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Step 1
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Step 2
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Step 3
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Step 4
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Image
Preparation
Material Selection
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Find
Minimum Exposure Needed to Print
Pure BLACK with the chosen
negative material
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Find
Ink Combination
for the Proper "Effective
Density" to Print Pure
White.
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Create
an Adjustment Curve
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Make a
negative
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